1. Field of the Invention
The present invention relates to a vehicular headlamp and a replacement method for a leveling actuator of the vehicular head lamp.
2. Description of Related Art
In a vehicular headlamp, a lamp unit that has a light source is disposed within an outer lamp casing including a cover and a lamp housing.
The lamp unit of a vehicular headlamp is sometimes provided with capability of both aiming adjustment that is initial adjustment of the light radiation direction by a light axis adjustment mechanism and leveling adjustment in which the inclination of the radiation direction depending on the weight of the load on the vehicle (e.g., Japanese Patent Application Publication No. 2004-227933 (JP 2004-227933 A)).
In the vehicular headlamp described in JP 2004-227933 A, the lamp unit is supported by a frame-shaped bracket that has a through hole that extends in the longitudinal direction, and the bracket is supported by the lamp housing via two adjustment shafts that each have a threaded shaft portion (screw portion) and one fulcrum shaft (drive shaft). Rear end portions of the fulcrum shaft and the two adjustment shafts are linked to the lamp housing, and a front end portion of the fulcrum shaft is linked to a lower end portion of the bracket. Front end portions of the two adjustment shafts are linked to an upper end portion of the bracket so as to be apart from each other in the lateral direction.
Furthermore, the fulcrum shaft is a drive shaft provided for a leveling actuator, and projects forward from a drive control portion of the leveling actuator. The drive control portion of the leveling actuator is attached to an external surface of the lamp housing.
In the vehicular headlamp, when one or both of the adjustment shafts are rotated so that the threaded shaft portion of the one or two adjustment shafts is screwed in or back out, the bracket and the lamp unit are tilted integrally as one unit in a horizontal plane or a vertical plane, with the fulcrum shaft serving as a fulcrum. Thus, lateral aiming adjustment or vertical aiming adjustment is performed.
On the other hand, when the drive shaft (fulcrum shaft) is moved in the longitudinal direction by drive force of the drive control portion of the leveling actuator, the bracket and the lamp unit are tilted integrally together in the vertical plane, with the two adjustment shafts serving as fulcrums. In this manner, leveling adjustment is performed.
As described above, in the vehicular headlamp described in JP 2004-227933 A, since the drive control portion of the leveling actuator is attached to the external surface of the lamp housing, the drive control portion is projected rearward from the lamp housing. Therefore, due to the projection of the drive control potion, a considerable space is needed in order to dispose the drive control portion, and impedes size reduction of the vehicular headlamp.
Therefore, among vehicular headlamps in which the lamp unit is disposed within the outer lamp casing as described above, there exists a vehicular headlamp whose size reduction is made possible by attaching the leveling actuator to the bracket and disposing the leveling actuator within the outer lamp casing.
In the vehicular headlamp, if the leveling actuator is broken, for example, it becomes necessary to perform a replacement operation of detaching the leveling actuator from the bracket and attaching a new leveling actuator to the bracket.
In such a case, however, in a construction in which the leveling actuator is disposed within the outer lamp casing as described above, the aforementioned replacement operation needs to be performed both inside and outside the outer lamp casing, which may reduce the ease of maintenance.